The Omega Men have had a lot of non-humanoid characters, and to really depict them correctly you need at least one really weird alien member. Elu certainly fits the bill, his weird indestructible energy-body making him a sort of living plot device. As a strange alien saved by the Omega Men, he's not going to be able to participate in their regular adventures, but he's still living on their ship, and a cool character to include just for the rare situations when he becomes an indispensable part of their crew.